| 摘要 |
Sulphuric acid is purified by passing hydrogen sulphide through the acid until the impurities are completely precipitated, filtering the acid, heating the filtered acid to a temperature above 80 DEG C., and again filtering it. The filtration steps may be carried out in a pressure filter of the kind described in Specification 322,091, [Class 46], using auxiliary filtering agents such as kieselguhr and fullers earth; the filter cake after being broken up can be repeatedly re-used. The acid may be cooled before the second filtration. If the acid to to be treated contains sulphur dioxide, this should be removed by blowing air or another inert gas into the acid prior to the process. The process is particularly applicable to acid of a concentration of greater than 70 per cent and removes impurities such as arsenic, selenium and copper. Examples are given. |
